The present invention relates generally to RF power amplifiers and more specifically to the use of a RF power amplifier including a synchronous buck DC-DC converter supplying power to a switched-mode power amplifier.
Electronic devices requiring use of a battery, such as mobile communications terminals, can achieve increased battery life by using efficient RF power amplifiers. RF power amplifiers typically have high current consumption. Attempts have been made using external circuitry to improve the efficiency of RF power amplifiers located on integrated circuits. However, internal switching frequencies can be orders of magnitude faster than off-chip signals. Therefore, external power supplies and control circuits are often unable to respond rapidly enough to varying load conditions. In addition, the parasitic resistance and inductance of the interconnects between an integrated circuit and external circuitry can reduce the voltage swing of the power amplifier, increase power loss and cause resonance and instability.